1. Field of the Invention
The present invention relates to metal-coated fibrous objects comprising a fibrous base material, such as raw fibers, yarns, fabrics and final textile products, and a layer of metal deposited thereon.
2. Description of the Prior Art
Vacuum deposition and electroless plating have been proposed as a means for the manufacture of metal-coated fibrous objects.
For example, a technique is known in which a thin layer of aluminum is formed on the surface of twisted yarns by vacuum deposition, and woven, knitted and nonwoven fabrics are made from the metal-coated yarns thus prepared. This method, however, can hardly be put into practical use because of poor adhesion of the aluminum layer to the substrate fiber; the deposited metal tends to become detached in the succeeding fabric making steps or when resulting fabrics are strongly rubbed. Furthermore, fabrics made of such yarns cannot be laundered because the deposited aluminum is removed almost completely by a single normal laundering.
Our study revealed that such troubles are caused by the facts that, in the vacuum deposition process, the energy of metal vapor bombarding the substrate fiber is too low to achieve sufficient adhesion and that light metals such as aluminum have poor resistance to acids and alkalis.
Another problem associated with vacuum deposition is that the metals that can be used are limited only to those which melt at relatively low temperatures and vaporize with relative ease. This eliminates the use of highly corrosion-resistant materials, such as stainless steel and tungsten.
Metal-coated fibrous objects made by electroless plating are also known. For example, dyed pieces of cloth are plated through immersion in an electroless plating solution, followed by several processing steps. This method is disadvantageous in that the discharged plating solution can cause pollution problems and hence a significant cost is added for the treatment of the used solution. In addition, this wet process requires drying and related steps, and suffers from deterioration of plated fabrics.
Other difficulties are that, although copper, nichel, chromium, cobalt and some other metals can be plated with comparative ease, the method is not applicable to alloys, the metals which are difficult to be put into solution, and the metals which are unstable in solution, and that firm attachment of metal layer to fiber substrate cannot be expected because the plated layer is likely to be thick.